Page 60 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

Common Preservatives

1- Sorbic acid

• This compound is a widely used preservative as the acid or its potassium
salt.
• Effective at low pH (≤ 4) and has good taste.

• syrups are usefully preserved with this agent.
• Used at 0.2% for fungi and bacteria.

2- Benzoic acid
• 0.2% in oral and topical formulations.
• Inactive at pH > 6.

3- parabens (Esters of P-hydroxybenzoic acid)

• Methyl (0.15-0.2%)  kill vegetative bacteria.
• Propyl (< 0.02%) inhibits molds
• Ethyl is effective for both.

• Their wide range of efficacy and stability make them popular
options and they are often used in combination due to
synergistic effects
• used as preservatives of emulsions, creams and lotions,

cosmetics, oral formulations.

4- Quaternary Ammonium Compounds

benzalkonium chloride:

• have broad spectrum antimicrobial activity
• used as preservatives in nasal, ophthalmic, and other topical preparations.
• not commonly used orally (bitter taste)

5- Phenolic Derivatives
• Phenol and phenolic derivatives such as m-cresol are commonly used as
preservatives in: -parenteral products - peptide and protein preparations

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